This invention relates to shuttleless weaving machines of a type having a nozzle for inserting a weft thread from a stationary yarn supply, a weft thread guide channel, a reed carried by a batten for beating-up the inserted weft thread, and a weft thread clamp or holder disposed between the yarn supply and the reed.
For a long time it was common practice with jet weaving machines of this type to mount the thread clamp or holder on the machine frame. However, after completion of the insertion of the weft and the closing of the thread clamp or holder, the reed is moved up to the fell of the cloth along with the inserted weft thread. This will cause an increase in the distance between the stationary thread clamp or holder and the crossing point between the weft thread and the edge of the warp thread array next to the thread clamp or holder. Therefore, when the thread clamp or holder is mounted in this manner the weft thread will be pulled back a certain distance from the shed during the beat-up and will be subjected to increased tension. This tension may lead to excessive stretching of the weft thread, particularly in the region between the thread holder and the neighboring end of the shed, and an excessively stretched weft thread tends to snap back when it is cut. This frequently leads to weft defects.
Attempts have been made to prevent the excessive stretching and the snapping-back of the weft thread by mounting the thread clamp or holder on the batten ahead of the thread entry opening. Although very good results have been attained through such positioning of the thread clamp or holder nonetheless with certain threads, particularly those with low twist and smooth surfaces, damage can occur in the region of the forward end of the weft thread, leading to weft defects. It has been assumed that these weft defects have their origins in the interaction between the fluid expelled by the nozzle and the weft thread, in the acceleration phase at the beginning of the insertion of the weft, and attempts have been made to improve the situation by modifying the nozzle. However, these attempts have not led to completely satisfactory results.
It is an object of the invention to prevent the referred-to damage of the weft thread. In doing this, the invention proceeds from the novel concept that even when the thread holder is mounted on the batten ahead of the nozzle the weft thread will still invariably be placed under tension to the extent that after it is cut it will snap back into the nozzle, whereby it is subject to damage, which damage may be so extensive that knots are formed in the weft thread.
In a non-previously-published prior patent application (European Pat. App. No. 80 10 3639.3) it was proposed to solve this problem by mounting the thread holder between the nozzle and the reed. With this positioning of the thread holder the weft thread is prevented from snapping back into the nozzle, thus avoiding all irregularities caused by such snapping back. This leads not only to improved protection and conservation of the weft thread and better fabric quality but also to an extension of the area of application of jet weaving machines which has not been regarded as possible heretofore, since under the proposed solution even slightly twisted and smooth yarn may be used for the weft thread.
The underlying object of the present invention is to refine this general arrangement in such a way that the leading end of the weft thread is expelled from the nozzle into the weft thread guide channel at a position which is as close as possible to the desired position with respect to the cross section of said guide channel transverse to the insertion direction.
This object is achieved according to the invention by disposing the thread clamp or holder in the nozzle itself.
In a preferred embodiment of the shuttleless weaving machine, in which the nozzle is furnished with a mixing tube on the side where the weft thread exits, the thread holder is disposed in that mixing tube.
As a result of the inventive disposition of the thread clamp or holder inside the nozzle or mixing tube, the nozzle and mixing tube may be positioned very close to the weft thread guide channel, whereby as a result of the short distance between the exit side of the mixing tube and the weft thread guide channel the probability that the weft thread will deviate transversely from its desired position with respect to the weft thread guide channel is greatly reduced. Furthermore, under this arrangement such deviations cannot be caused by a thread holder disposed between the mixing tube and the weft thread guide channel, because there is no thread holder disposed in this region.